Flexible automotive assembly workstation and method

ABSTRACT

An apparatus for assembling multiple automotive body styles on a single assembly line. The apparatus includes a workstation with multiple geometry fixtures, at least one geometry fixture for each automotive body style to be processed at the work station. One geometry fixture is at a ready position of the work station to support an automotive component during a processing operation. The geometry fixtures can be exchanged at the ready position so that a production rate of the assembly line can be maintained. The apparatus also includes a lowerator for transferring an automotive component from an overhead transport system to the geometry fixture at the ready position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Provisional PatentApplication Serial No. 60/180,607, filed Feb. 7, 2000. This applicationis filed contemporaneously with two other applications, “FLEXIBLEAUTOMOTIVE ASSEMBLY LINE AND METHOD”, and “INTERCHANGEABLE NESTS FORSUPPORTING COMPONENTS ON A TRANSPORT SYSTEM”.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for the flexibleassembly of a plurality of automotive body styles on a single assemblyline with zero loss of production during changeover.

BACKGROUND OF THE INVENTION

Current body assembly lines typically use a palletized approach forassembling components of the automotive body style to be built and forjoining those components to one another at a framing station. Thepalletized approach requires that sufficient pallets be provided foreach type of body style to be assembled and transported along theassembly line at one time, including spares for any pallets that may bedamaged during the assembly process. When this number is multiplied bythe number of models to be produced on the assembly line, the number ofpallets can be a very large number requiring large amounts of off linestorage space and also requiring a tremendous amount of maintenance tomaintain the accurate geometry required of a palletized fixture.

SUMMARY OF THE INVENTION

It would be desirable to reduce the number of pallets required for amodern automotive assembly line capable of producing a plurality ofautomotive body styles on the same line without any loss of productionduring changeover. It would be desirable in the present invention toprovide an assembly line configuration capable of building a singleautomotive body style, two automotive body styles, three automotive bodystyles, or four automotive body styles without loss of production, andwithout requiring excessive changes in the production lineconfiguration. It would be desirable in the present invention to providean overhead component delivery system for the early stages of theassembly line, while providing a palletized transportation systembetween the workstation beginning at the underbody respot station. Itwould be desirable to provide an overhead transport system for thecomponent assembly line which is capable of quick and efficientchangeover of body style fixtures to produce different body styleswithout interruption of production. It would be desirable to provide aflexible assembly workstation having an interchangeable workpiecesupport or geometry fixture for the different body styles to bemanufactured through the workstation, where the different supportfixtures can be interchanged with one another without loss ofproduction.

A flexible automotive body assembly line according to the presentinvention includes an overhead component transport system. The overheadtransport system preferably is provided for the bodyside left handassembly line, bodyside right hand assembly line, and underbody assemblyline and tack workstation. After the underbody is tacked at theunderbody tack workstation, the underbody is transported by an overheadtransport system and transferred to a palletized system at the underbodyrespot workstation. After respot, the pallet system transfers theunderbody to the framing workstation, where the bodyside left and righthand components are delivered by the overhead system. The framingworkstation positions the left hand and right hand components of thebodysides to the underbody and tacks the right and left components withrespect to the underbody. The pallet then transfers the assembledworkpiece to the roof framing fixture and continues through the framingrespot workstation where additional welding and tacking is performed.The pallet system then transfers the assembled framed body to closureworkstations where closure panels can be assembled prior to deliveringthe assembled body to the paint station.

Preferably, the overhead delivery system for the bodyside left handassembly line, the bodyside right hand assembly line, and the underbodytack workstation is an electric monorail system. The electric monorailsystem can provide an overhead rail extending between the variousworkstations, and preferably extends in a circular or loop configurationpassing through the workstations and through a workpiece support orantler exchange workstation for preparing the overhead delivery systemto receive and transport different body styles or models through theassembly line without any loss of production. The electric monorailsystem can include a carriage powered by an electric motor for movementbetween the workstations along the overhead monorail. Downwardlyextending supports or pillars extend from the carriage for receiving theworkpiece support or antlers there between. The workpiece supports orantlers are interchangeable as required for engaging the particular bodystyle or model of components to be manufactured through the assemblyline. The vertically extending supports or pillars include a telescopingfunction to allow the workpiece support or antlers to be moved from avertically raised position used to transport the workpiece or componentsbetween workstations, and a vertically lowered position at a workstationto deliver the workpiece or a component to the workpiece support, nestor geometry fixture at the particular workstation. The verticallyextending supports or pillars also include latching mechanisms to holdthe workpiece support or antlers in the raised position during transportbetween workstations. Preferably, the drive for unlatching and loweringthe workpiece support or antlers and supported workpiece or component isprovided at each workstation, and includes a single drive for eachvertically extending support or pillar of the electric monorail carriagesystem. Preferably, the single drive for each vertically extendingsupport or pillar of the carriage located at the workstation is capableof unlatching the latch mechanism prior to lowering the workpiecesupport or antlers at the workstation location, and after the work hasbeen performed at that workstation raising the work support or antlerportion of the carriage to the raised position and latching the latchmechanism of the vertically extending support or pillars from thecarriage prior to the carriage leaving the workstation.

The present invention also includes a flexible body assemblyworkstation. For purposes of illustration, a single workstation will bedescribed. The flexible body assembly workstation can be used at thebodyside left hand assembly location, the bodyside right hand assemblylocation, the underbody tack assembly workstation, or any other majorsubassembly component. The workstation preferably includes an overheadcomponent delivery system extending through the workstation. Theoverhead delivery system can enter the workstation empty, or can delivera partially completed component to the workstation for additionalassembly steps. In either case, a workpiece support or geometry fixtureis provided at the flexible body assembly workstation for receiving theparts to be built up into the component to be transported, or to beadded to the partially completed component delivered by the overheadsystem. The workpiece support or geometry fixture at each flexible bodyassembly workstation is interchangeable to match the body style or modelto be manufactured at the workstation for that particular operationcycle. Preferably, the flexible assembly workstation includes sufficientcapacity to handle up to four different workpiece support or geometryfixtures for use on demand at the workstation depending on theparticular body style or model to be manufactured at the workstation. Inone configuration, the workpiece supports or geometry fixtures areconnected to a delivery system capable of moving the fixtures betweenthe standby or storage positions and a ready position for receiving theworkpiece component to be delivered to the workstation. In thealternative, a workpiece support or geometry fixture can be deliveredusing an “H-Gate” configuration. The H-Gate delivery system uses alinear transfer system, such as a rail delivery to the workstation readyposition and between two standby or storage positions on either side ofthe station. The standby positions are serviced by two transverselyextending delivery systems. One delivery system is provided on each sideof the workstation producing the “H” configuration for which the systemis named. The transversely extending delivery systems provide, orpre-load, the next workstation support or geometry fixture required atthe workstation. For changeover, the current workpiece support orgeometry fixture and the new workpiece support or geometry fixture arereciprocated simultaneously along the rail system bringing the newworkstation support or geometry fixture into the workstation andremoving the previously used workpiece support or geometry fixture fromthe workstation. When properly located, the rail transfer system stopsin the appropriate position for the geometry fixture to be positioned atthe workstation. The old workpiece support or geometry fixture is thenremoved from the standby position by one of the transversely extendingdelivery systems. The process is then repeated by pre-positioning thenext desired geometry fixture at one of the standby positions forsubsequent delivery to the workstation on demand.

Other objects, advantages and applications of the present invention willbecome apparent to those skilled in the art when the followingdescription of the best mode contemplated for practicing the inventionis read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a perspective view of the present invention, shown in anexemplary operational environment;

FIG. 2 is a lateral elevational view of the present invention, shown inan exemplary operational environment;

FIG. 3 is an end elevational view depicting the lowerator mechanism ofthe present invention;

FIG. 4 is a detailed cross-sectional view of the latch means of thepresent invention;

FIG. 5 is a detailed perspective view of the latch means and loweratormechanism of the present invention;

FIGS. 6A-6C provide detailed elevational views of the loweratormechanism in operation;

FIG. 7 is a side elevational view of the preferred embodiment of alowerator according to the present invention;

FIG. 8 is a detailed perspective view of the preferred embodiment of thelowerator according to the present invention;

FIGS. 9A-9C are detailed cross-sectional illustrations of the latchmechanism and actuator of the preferred embodiment of the loweratoraccording to the present invention;

FIG. 10 is a simplified schematic diagram of a vertical position sensoraccording to the present invention;

FIG. 11 is a simplified flow diagram of a control method for a loweratoraccording to the present invention;

FIG. 12 is a simplified schematic illustrating the overhead transfersystem for component parts to the point where the underbody is put on apallet system at the underbody respot workstation, and the bodysidepreassemblies are attached to the underbody at the framing workstation;

FIG. 13 is a perspective view of a lowerator for transporting theunderbody to and from the underbody tack workstation;

FIGS. 14A-14E are perspective views of various embodiments of anoverhead delivery system with interchangeable workpiece supports orantler configurations for different body styles or models;

FIG. 15 is a perspective view of an assembly line portion with anoverhead delivery system passing through a workpiece support or antlerexchange workstation, where the workpiece support or antlers can bechanged over to a new body style or model configuration duringproduction and a perspective view of an H-Gate delivery system for awork support or geometry fixture at a welding workstation;

FIG. 16 is a side elevational view of a workpiece support or antler ortray style selection apparatus for removing a previously used workpiecesupport or antler configuration and installing a new workpiece supportor antler configuration for a new body style or model;

FIG. 16A is a perspective view of a robot for exchanging an antler nestwith respect to a carrier;

FIG. 17 is a perspective view of loading stations, either manual orautomated, positioned between two flexible body assembly workstations;

FIG. 18 is a perspective view of a load and/or unload automatedworkstation for the overhead delivery system between flexible bodyassembly workstations according to the present invention;

FIG. 19 is a perspective view of a flexible body assembly workstationaccording to the present invention having a plurality of welding robotspositioned about the workstation, and overhead delivery system, and aninterchangeable workpiece support or geometry fixture at theworkstation;

FIG. 20 is a plan view of the flexible body assembly workstationillustrated in FIG. 19;

FIG. 21 is a plan view of an “H-Gate” workpiece support or geometryfixture configuration as an alternative for supplying the appropriateworkpiece support to the flexible body assembly workstation as requiredfor the particular body style or model to be manufactured;

FIG. 22 is a side elevational view of the H-Gate delivery systemillustrated in FIG. 21;

FIG. 23 is a simplified H-Gate cross section illustrating the overheaddelivery system and the H-Gate delivery system to the flexible bodyassembly workstation;

FIGS. 24A-24D illustrates alternative configurations for the H-Gatedelivery system for the workpiece support or geometry fixture tooling tothe flexible body assembly workstation according to the presentinvention allowing flexible set up between one model, two models, threemodels, and four models through the same flexible body assemblyworkstations; and

FIG. 25 is a perspective view of a palletized system for delivery of theunderbody to the respot workstation and on to the framing workstation,framing respot workstation, closure workstation, and paint workstation.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, the present invention generally includesworkpiece conveyance means 10 for transporting a workpiece along pathmeans 12 for defining a path of travel between workstations 14positioned along the path means, and locator means positioned at theworkstation and operative for locating the workpiece at the workstation.A lowerator 18 is provided for moving the workpiece between theconveyance means 10 and the locator means. For purposes of illustration,the lowerator 18 is shown in combination with an assembly systemincluding the path means 12 and workstations 14. The conveyance means 10transports workpieces between the workstations 14, where one or morespecific processing operations are performed on the workpieces. Forinstance, the assembly system can be in the form of an automotiveproduction line where workpieces, such as automotive body panels andframe components, are progressively assembled at the workstations 14along the path 12 of travel. While a particular operational environmentis illustrated herein, it is not intended to be limiting with respect tothe present invention, which will have numerous applications asunderstood by those of skill in the art.

More particularly, the path means 12 can include at least one rail 20,such as an overhead monorail, suspended from a support structure such asa coextensive horizontal spine 22 and intermittently spaced verticalsupports 24. The workpiece conveyance means 10 includes driving means inthe form of a motor-driven trolley 26 operative to move the conveyancemeans 10 along the rail 20 in known fashion. As with other aspects ofthe depicted operational environment, the illustrated driving means arenot intended to be limiting with respect to the present invention, andany desired driving means can be adopted to serve the purpose of movingthe conveyance means 10 along the selected path means 12 in the desiredoperational environment.

Referring now to FIGS. 2 and 3, the workpiece conveyance means 10generally includes both the trolley 26 and a carrier 28. The trolley 26is configured generally in an inverted “U” shape, with horizontal andvertical members. The horizontal member is fixed to a parallel-disposedsupport cross-piece providing a point of attachment for trolley 26 orother driving means as appropriate. The trolley 26 is thus immovablyassociated with the driving means and moves along the path means 12 inconjunction therewith. The carrier 28 is also generally in a “U” shape,including a horizontal member and a vertical member. Workpiece carryingmeans, such as carrier 28, in the form of a workpiece nest can include aplurality of projecting fingers or antlers disposed on a horizontalelement of the carrier 28 to support the workpiece being conveyed. Theconfiguration of the workpiece nest can take any form desired andappropriate for the workpiece to be conveyed and the work to beperformed thereon. Each of the trolley 26 and carrier 28 may includelengths of metal plates, beams, brackets, or tubing joined by welding,joining plates, or other known means, though other suitably strongmaterials can be substituted.

As indicated, the carrier 28 is slidingly associated with trolley 26 soas to be moveable vertically in relation to the trolley 26 in order tolower a workpiece into the workstation 14 without the necessity oflowering the entire conveyance means 10 and a section of the rail means20, as with some prior known mechanisms. Bearing blocks 30 are provided,one associated with each of the vertical members, the bearing blocksbeing dimensioned to slidingly receive the vertical elements 34 of thecarrier 28 therein. Referring now to FIG. 4, bearing surfaces 32 areprovided along the length of vertical elements 34 to define a travelsurface for sliding movement of the carrier 28.

Means 36 are provided associated with the carrier 28 for receiving thepositioning means 38. Referring now to FIGS. 2 and 4, receiving means 36can include a cam surface 40, such as a channel or slot, preferablyprovided at both ends of the horizontal member 42 of the carrier 28. Camsurface 40 is fashioned from metal or other suitably strong material.The cam surface 40 illustrated in FIGS. 1-2 and 4-6C includes an outertravel surface extending beyond the channel opening to define a radiusedportion 44. The cam surface 40 is fixed between plates 48 connected tothe horizontal member 42 of the carrier 28. The plates 48 includecut-out portions 50, leaving a sufficient length of each cam surface 40unobstructed for movement of the positioning means 38 there along. Thecam surface 40 opens outwardly away from each end of the carrier 28. Thecam surface 40 is dimensioned to receive therein a lifter roller 52 ofthe positioning means 38.

For travel between workstations, the carrier 28 is supported in avertically raised condition on the trolley 26 by latch means 54.Referring now to FIGS. 2-4, and more particularly to FIG. 3, the latchmeans 54 can include a latch arm 56 operatively connected to a lever arm58 by a transfer link 60. The latch arm 56 pivots about a fixed pointdefined by a pivot pin 62 extending between parallel plates 48 connectedto the trolley 26 as shown in FIG. 4. A pin-receiving portion 64 of thelatch arm 56 receives therein a pin 66 fixed to the parallel plates 48provided on the carrier 28. The lever arm 58 is pivotally mountedoutside of one of the plates 48 about a fixed pivot point 68. The leverarm 56 is preferably biased, such as by a spring means 70, or the like,towards the position shown in FIG. 3.

In the embodiment shown in FIGS. 4-5, the lowerator 18 is shown providedat a workstation 14. The workstation 14 is shown with a base 72, andaccording to this embodiment, the lowerator 18 is fixedly mounted to thebase 72 by appropriate support structure 74. The lowerator 18 caninclude a lifter arm 76 adapted for rotational movement. A roller 78 isrotatably mounted adjacent the terminal free end of the lifter arm 76.The roller 78 is receivable with respect to the cam surface 40, such asthe illustrated channel. Means 80 for actuating the latch means 54 isprovided adjacent the terminal end of the lifter arm 76, and extendsradially outward from lifter roller 78. The latch actuating means 80 caninclude an actuator pin 92 projecting to engage the lever arm 58. Thelowerator 18 is preferably motor-driven, and a motor 82 and gearbox 84are provided in operative association with the lifter arm 76. The motor82 can be powered by any desired conventional means. The radialdimensions of lifter arm 76 are such that, during rotational movementthereof, roller 78 is received with respect to the cam surface 40, suchas the channel of the carrier 28, when the conveyance means 10 ispositioned at the workstation 14.

Referring now to FIGS. 2 and 5, the lowerator 18 is provided inalignment at opposite ends of the conveyance means 10. The lowerator 18is positioned at an appropriate workstation 14 in relation to the pathof travel of the conveyance means 10 such that, after arrival of theconveyance means 10 at the workstation 14, rotational movement of thelifter arm 76 brings the roller 78 into contact with the cam surface 40,such as the channel of the carrier 28. As best seen in FIG. 5, guidemeans 86 is disposed at the workstation 14 to facilitate properalignment of the lowerator 18 with the conveyance means 10, and prohibitunwanted lateral movement of the conveyance means 10 during operation ofthe lowerator 18. These guide means 86 can include horizontally orientedguide rollers 88 arranged on support posts 90 in opposing fashion oneither side of horizontal member of the carrier 28 to define a paththere between for receiving the conveyance means 10. Two such pairs ofguide means 86 are preferably provided, one pair at predeterminedlocations of each end of the horizontal member when the conveyance means10 come to a stop at the workstation 14.

Referring now to FIGS. 6A-6C, after arrival of the conveyance means 10at the appropriate workstation 14, rotational movement of the lifter arm76 commences. In the lowering cycle of operation, the lifter arm 76rotates forwardly from a start position, shown in FIG. 4, bringing theroller 78 into engagement with the cam surface 40, such as theillustrated channel of the carrier 28, best seen in FIG. 6A. Withcontinuing rotational movement of the lifter arm 76, the roller 78circumscribes an arcuate path while moving upwardly within theillustrated channel, where the roller 78 engages cam surface 40 to urgethe carrier 28 vertically upwards until reaching the maximum verticalheight of the arc as best seen in FIG. 6B. This action drives the latchpin 66 upwards and out of engagement with the latch arm 56. Simultaneouswith the upwards movement of the carrier 28, actuator pin 92 actuatesthe lever arm 58, urging the lever arm 58 to pivot about an axis in afirst, clockwise direction. The rotation of the lever arm 58 urges thetransfer link 60 in an outward direction “A” away from the pin 66 todraw the latch arm 56 out of the vertically downward path of travel ofthe pin 66. Continued forward rotational movement of the lifter arm 76effects vertically downward movement of the carrier 28 relative to thetrolley 26, until the carrier 28 is brought into position at theworkstation 14 as best seen in FIG. 6C. Locator pins (not shown) may beprovided at the workstation as necessary to receive the workpiece and/orcarrier 28. It will be appreciated that the length of the cam surface40, such as the channel of the carrier 28, is sufficient to provide forunimpeded movement of the roller 78 throughout the range of motion ofthe lifter arm 76, both in the counter clockwise direction, and forraising the carrier 28 to the latched position, the clockwise direction.

From the foregoing it will be appreciated that the operation of raisingthe carrier 28 into latched engagement with the trolley 26 takes placeaccording to the foregoing description, except in reverse order ofoperation and with the lifter arm 76 rotating clockwise. Additionally,the latch arm 56 is not retracted by actuation of the lever arm 58during the raising operation. As indicated, the lever arm 58 is biasedtowards its default position after the actuator pin 92 moves out ofengagement therewith during the lowering operation. The latch arm 56 isthus positioned in the vertically upward path of travel of the pin 66.The latch arm 56 is provided with a ramped travel surface 94 for the pin66. The ramped surface 94 is angled such that engagement of the latchpin 28 with the ramped surface 94 urges the latch arm 56 to pivotoutward in direction “A” until the latch pin 66 passes out of engagementwith the ramped surface 94, and the spring means 70 urges the latchmeans back to a biased position so that the latch pin 66 can be broughtinto engagement with the pin-receiving portion 64 of the latch arm 56 asthe roller 78 moves through an arcuate path in the clockwise direction.

Those of skill in the art will appreciate that the harmonic motion ofthe carrier 28 brought about by the arcuate rotational path of thelifter arm 76 results in a so-called “soft touch” motion of the carrier28 proximate the upper and lower limits of vertical range of motion.This “soft touch” motion is beneficial in reducing wear and tear on thelowerator 18, as well as providing for the relatively delicate handlingof the workpiece.

Referring now to FIGS. 7-11, and more particularly FIGS. 7 and 8, thepreferred embodiment of a lowerator 18 a according to the presentinvention is illustrated. The present invention discloses an apparatusfor transporting at least one workpiece along at least one rail 20 adefining a path 12 a of travel through a workstation 14 a. While thepresent invention preferably includes a single electric monorailoverhead system, the invention contemplates application to other knownconfigurations of workpiece conveyors including multi-rail, bothelectric and non-electric, or non-electric monorail configurations. Inthe preferred configuration, a trolley 26 a is movable along the rail 20a and is controllable to stop at the workstation 14 a by appropriateswitches and/or sensors and control circuitry as is known to thoseskilled in the art. A carrier 28 a is connected to the trolley 26 a forsupporting at least one workpiece during movement of the trolley 26 aalong the rail 20 a with respect to the workstation 14 a. The carrier 28a is movable between a raised position, illustrated in FIGS. 7 and 8,and a lowered position, shown in phantom in FIG. 7, when positioned atthe workstation 14 a. At least one latch 54 a is provided formaintaining the carrier 28 a in the raised position with respect to thetrolley 26 a when the latch 54 a is in the locked position. The latch 54a allows movement of the carrier 28 a to the lowered position when thelatch 54 a is in the released position. An actuator 16 a is provided foreach latch 54 a. Each actuator 16 a is movable from a first position toa second position. As the actuator moves from the first position to thesecond position, the actuator 16 a engages the carrier 28 a, releasesthe latch 54 a, and lowers the carrier 28 a to the lowered position.While moving in the reverse direction from the second position to thefirst position, the actuator 16 a raises the carrier 28 a, locks thelatch 54 a, and disengages from the carrier 28 a.

Preferably, the actuator 16 a is supported separate from the rail 20 a.In the preferred configuration, the actuator 16 a is supported from thefloor or base 72 a of the workstation 14 a. The actuator 16 a has a camfollower or roller 78 a connected to one end of a rotatable crank arm 76a. The cam follower is engageable with a cam surface 40 a formed on thecarriage 28 a. The cam follower 78 a is engageable with the cam surface40 a when the carriage 28 a is stopped at the workstation 14 a.Preferably, the cam follower 78 a is in the form of a roller having aninner cylindrical spool surface positioned between radially enlargedflange members capable of guiding and maintaining the carrier 28 a inoperative contact with the cam follower 78 a as the carrier 28 a ismoved between the raised position and the lowered position. In thepreferred configuration, the cam surface 40 a is formed as a bottomsurface of the carrier 28 a.

Referring now to FIGS. 7-9C, and more particularly to FIGS. 9A-9C, thepreferred embodiment of the latch 54 a includes a second cam engagingsurface 40 b for actuating the latch between the locked position and thereleased position. The latch 54 a is rotated in response to engagementof the second cam surface 40 b by the cam follower 78 a as the camfollower 78 a simultaneously moves along the first and second camsurfaces 40 a, 40 b. In the illustrated embodiment, the latch 54 a ispivotally connected to the carrier 28 a. A pair of telescoping posts orvertical elements 34 a connect the carrier 28 a to the trolley 26 a.Slide blocks or bearing blocks 30 a are enclosed within the telescopingposts 34 a to prevent infiltration of foreign matter, while guidingmovement of the carrier 28 a with respect to the trolley 26 a.

In the preferred configuration, best seen in FIGS. 9A, 9B and 10, atleast one position sensor 96 a, 96 b, and 96 c is supported with respectto the telescoping post 34 a for generating a signal corresponding to aretracted and locked position of the post (illustrated in FIG. 10 insolid line). The position sensor 96 a can be supported with respect tothe post 34 a to sense the position of the telescoping portion of thepost 34 a relative to the stationary portion 35 a, as shown in FIG. 10.Alternatively or additionally, the sensor 96 b can be supported withrespect to the telescoping portion of the post 34 b to sense theposition of a surface 67 of the latch 54 b, as shown in FIG. 9A. Thesensor 96 b can be mounted to the stationary portion 35 b with a bracket99. Alternatively or additionally, the sensor 96 c can be supported withrespect to the telescoping portion of the post 34 c to sense theposition of a tip 69 of the latch 54 c, as shown in Fib. 9B. The sensor96 c can be mounted to the stationary portion 35 b of the post 34 c witha bracket 101. The sensors 96 b and 96 c can be positioned approximatelyone eighth of an inch (⅛″) away from the surface 67 and the tip 69,respectively, when the latch 54A is in a locked position. The sensors 96a, 96 b and 96 c are shown schematically in FIGS. 10, 9A and 9Brespectively. Control means 98 a, 98 b, and 98 c such as one or morecontrol circuits, is provided for receiving the signal from one or moreof the position sensors 96 a, 96 b, and 96 c for processing signals inaccordance with a program stored in memory. Means 100 a is provided forsensing if the carriage or workpiece conveyance means 10 a is at theworkstation 14 a. If the carrier 28 a is at the workstation 14 a, thecontrol means 98 a (FIGS. 7 and 10) determines if the latch 54 a is inthe locked position. If the latch 54 a is not in the locked position,the control means 98 a generates an error signal. If the latch 54 a isin the locked position, the control means 98 a actuates the actuator 16a in a first direction of travel moving from the first or start positionto an intermediate position. When the actuator 16 a is in theintermediate position, the control means 98 a determines if the latch 54a has been released from the locked position. If the latch 54 a is stillin the locked position when the actuator 16 a is in the intermediateposition, the control means 98 a generates an error signal. If the latch54 a is in the released position when the actuator 16 a is in theintermediate position, the control means 98 a continues actuation of theactuator 16 a from the intermediate position to a second positioncausing the carrier 28 a to move from the raised position to the loweredposition. After work has been performed on the workpiece at theworkstation 14 a when the carrier 28 a is in the lowered position, thecontrol means 98 a actuates the actuator 16 a in a second direction oftravel to move from the second position to the first position. When theactuator 16 a has returned to the first position, the control means 98 adetermines if the carrier 28 a is in the raised and locked positionthrough the position sensor 96 a. If the carrier 28 a is not in theraised and locked position when the actuator 16 a is in the firstposition, the control means 98 a generates an error signal. If thecarrier 28 a is in the raised and locked position when the actuator 16 ais in the first position, the control means 98 a generates a signal foractivating the motor driven trolley 26 a for moving the carriage 28 afrom the workstation 14 a.

In operation, conveying means such as trolley 26 a is driven along railmeans defining a path of travel with respect to a workstation 14 a. Theconveying means includes a carrier 28 a for supporting at least oneworkpiece for delivery to the workstation 14 a. As the trolley 26 a andcarrier 28 a approach the workstation 14 a, the carrier 28 a operablyengages guide means 86 a for aligning and orienting the carrier 28 a inthe proper position as the carrier 28 a enters the workstation 14 a foroperative engagement with the lowerator 18 a located at the workstation14 a. The guide means 86 a can include a pair of converging guide railsto direct the leading edge of the carrier 28 a into the proper positionas the carrier 28 a enters the workstation 14 a, and/or can include apair of rollers 88 a rotatably supported on posts 90 a for guiding theleading edge of the carrier 28 a into the proper orientation as itenters the workstation 14 a.

When the trolley 26 a has reached a predetermined position at theworkstation 14 a, the motor driven trolley 26 a is stopped and a signalis generated by a sensor 100 a indicating that the carrier 28 a is atthe workstation. The signal is received by the control means 98 a andprocessed according to a control program stored in memory. The controlprogram can include the steps illustrated in FIG. 11. Initially, theprogram determines if the carrier 28 a is at the workstation in querystep 200. If a signal indicating that the carrier 28 a is at theworkstation 14 a is not received, the program branches back to reiteratethe same query in step 200. When a signal is received from the sensor100 a indicating that the carrier 28 a is at the workstation 14 a, theprogram continues to the next query step 202 to determine if theposition sensor 96 a indicates that the carrier 28 a is in the raisedand locked position. The position sensor 96 a can be in the form of aproximity sensor as illustrated in FIG. 10 positioned appropriately tooperatively indicate the presence of a radially extending metal portionof the post 34 a when in the raised and locked position as illustratedin solid line. If the position sensor 96 a is not generating a signal,the control program branches to generate an error signal in step 204indicating that a sensor failure has occurred. After indicating thatthere is a sensor failure, the program continues to step 206 wherefurther operations are stopped pending operator determination of thecause of the sensor error reported in step 204. If a signal is receivedfrom the position sensor 96 a indicating that the carrier 28 a is in theraised and locked position, the program continues on to step 208 wherethe motor 82 a is activated in order to drive the lifter arm 76 athrough gear box 84 a to bring the cam follower or roller 78 a intooperative engagement with the first cam surface 40 a formed on thebottom of the carrier 28 a. Preferably, the lifter arm 76 a is driven ina first rotational direction and engages the bottom of the carrier 28 aprior to reaching the upper limit of travel through the defined arc ofrotation. As best seen in FIG. 9A, as the lifter arm 76 a continues torotate from the start position, and when at approximately 16° ofrotation, the roller 78 a has lifted the carrier 28 a a sufficientdistance to relieve the weight from the latch 54 a, or approximately0.375 inches. As the roller 78 a is raising the carrier 28 a, the roller78 a simultaneously engages the second cam surface 40 a as the roller 78a continues to engage the first cam surface 40 a. The lifting motion ofthe carrier 28 a raises the latch 54 a a sufficient distance to removethe pin 66 a from the pin-receiving portion 64 a of the latch arm 56. Asthe carrier 28 a is being lifted by the roller 78 a, the outwardlyextending metal portion of the post 34 a is also raised and moved towardthe position shown in phantom in FIG. 10. As the roller 78 a reaches theupper limit of travel, the radially outwardly extending metal portion ofthe post 34 a reaches the position shown in phantom and the signal fromthe position sensor 96 a is lost or discontinued. The uppermost positionof the roller 78 a is shown in FIG. 9B where the roller 78 a hascontinued simultaneous contact with the first and second cam surfaces 40a, 40 b and is in the process of rotating the latch arm 56 a about thepivot 62 a to unlatch the carrier 28 a from the trolley 26 a. When inthis uppermost or intermediate position, the control program proceeds tothe next query step 210 to determine if the position sensor signal hasbeen discontinued. If the signal from the position sensor 96 a is stillpresent, the program branches to step 212 to indicate a sensor and/orrelease error, since the carrier 28 a has not been raised a sufficientdistance to unlatch the carrier 28 a from the trolley 26 a and continuedmovement would therefore cause damage to the conveying structure. Theprogram then continues on to the stop step 206 where no further actionis taken until an operator determines the cause of the error. If thesignal from the position sensor 96 a has been discontinued, the controlprogram continues on to step 214 where rotation of the lever arm 76 acontinues without stopping through the intermediate position to rotatethe actuator to the lowest position placing the carrier 28 a in theposition shown in phantom in FIG. 7. As the roller 78 a passes throughthe intermediate position, the simultaneous engagement with the firstand second cam surfaces 40 a, 40 b rotates the lever arm 56 a asufficient distance to completely release the pin 66 a and bypass thepin as the carrier 28 a is lowered. The position of the roller 78 aillustrated in FIG. 9C is approximately 45° from the start position andthe carrier 28 a has been lowered approximately 0.375 inches down fromthe fully raised position. When the carrier 28 a is in the lowestposition, work is performed on the workpiece or workpieces that havebeen transferred to the workstation 14 a. After completion of the workbeing performed at the workstation 14 a, an appropriate signal is sentto the control means 98 a and the motor 82 a is activated in the reversedirection to move the lifter arm 76 a through the gear box 84 a from thelowest or second position back toward the first or start position. Thepause for work to be performed is illustrated in step 216 of the controlprogram followed by step 218 indicating reverse rotation of the actuatorto the start position. When rotating in the reverse direction, theroller 78 a passes through the reverse order of movement previouslydescribed, first reaching the position illustrated in FIG. 9C, then FIG.9B, followed by FIG. 9A, and finally back to the start positionillustrated in FIGS. 7 and 8. When in the start position, the radiallyoutwardly extending metal portion of the post 34 a has returned to thesolid line position illustrated in FIG. 10, and the control programcontinues to query step 220 to determine if the position sensor 96 a isgenerating a signal to the control means 98 a. If no signal is receivedfrom the position sensor 96 a, the control program branches to step 222where an error signal is generated indicating a sensor or lock error.The program then continues on to the stop step 206 where no furtheraction is taken until the cause of the error is determined by anoperator. If the signal from the position sensor 96 a is received by thecontrol means 98 a, the program branches to the step 224 allowing themotor trolley 26 a to be energized to remove the carrier 28 a from theworkstation 14 a. Preferably, biasing means 102 a is provided for urgingthe lever 56 a toward the unlocked position of rotation with respect topivot pin 62 a. In the preferred configuration, the lower portion of thecarrier 28 a is formed as a box beam having a cutout portion forreceiving the rotatable latch arm 56 a.

The present invention discloses a simple, efficient, and reliableassembly system including an overhead rail means defining a path oftravel with respect to a workstation, and means for conveying aworkpiece along the rail means. The conveying means according to thepresent invention includes a carrier for supporting at least oneworkpiece for delivery to the workstation, where the carrier is movablyassociated with the conveying means so as to be vertically positionablebetween raised and lowered positions with respect to the conveyingmeans. A lowerator according to the present invention automaticallymoves the carrier between the raised and lowered positions. Latch meansis provided for securing the carrier to the conveying means in theraised position for transport to and from the workstation. At least onelifter defines a path of travel in first and second directions, whereduring movement in the first direction the lifter actuates the latchmeans to uncouple the carrier from the conveying means, for movementinto the lowered position, and where during movement in the seconddirection the lifter lifts the carrier from the lowered position to theraised position and actuates the latch means so as to secure the carrierto the conveying means in the raised position.

In the preferred configuration, at least two vertically extendingmembers or posts are provided at opposite ends of the carrier, and alatch and position sensor is associated with each post, where theposition sensor can signal if the carrier has been raised and placed inthe locked position prior to transport out of the workstation, and canalso determine if the carrier has been raised sufficiently and unlatchedprior to movement of the carrier into the lowered position. If either ofthe sensors does not generate the appropriate signal, the controlprogram automatically stops further actuation of the loweratormechanism. It is believed that only one sensor is required for each postin order to determine the position of the vertical member and the latch,however multiple sensors could be provided for additional signals to thecontrol means without departing from the spirit and scope of the presentinvention.

Referring now to FIG. 12, a simplified schematic diagram of the overallbody assembly line 300 is illustrated. Solid lines between boxesrepresent transport of parts between boxes with an overhead transportsystem. Double lines between boxes represent transport of parts with apallet transport system. The bodyside left hand panel assembly line isillustrated as a single box 302 in this simplified schematic drawing.The bodyside right hand assembly line is illustrated as a single box 304in this diagram. Box 306 illustrates the entire underbody assembly lineand tack weld station in this diagram. In the preferred configuration,the bodyside left hand assembly line 302, bodyside right hand assemblyline 304, and underbody assembly line 306 through the tack weldworkstation are part of individual overhead transport systems for eachof the lines illustrated as ovals in the schematic drawing numbered 308,310, and 312 respectively. The first overhead transport system 308delivers parts or components in various stages of assembly along thebodyside left hand assembly line 302 between the various workstations.

Preferably, the first overhead transport system 308 is a closed loopsystem passing through the various workstations and passing through aworkpiece support for antler exchange workstation, where the workpiecesupport or antlers can be exchanged depending on the body style or modelto be assembled through the assembly line without interruptingproduction. The first overhead transport system 308 can be supplied withsubassemblies from at least one subassembly line 303 having an overheadtransport system 305.

The overhead transport systems 308, 305 can be independent from oneanother or can be integrated into a single overhead transport system.The second overhead transport system 310 transports parts or componentsin assembled or partially assembled states between the variousworkstations of the bodyside right hand assembly line 304. Preferably,the second overhead transport system 310 is a closed loop system passingthrough each of the workstations of the bodyside right hand assemblyline 304 and through a workpiece support or antler exchange workstation.The second overhead transport system 310 can be supplied withsubassemblies from at least one subassembly line 307 having an overheadtransport system 309. The overhead transport systems 309, 310 can beindependent from one another or can be integrated into a single overheadtransport system. At the workpiece support or antler exchangeworkstation, the workpiece support or antlers carried by each overheadtransport system carriage can be changed as required depending on thebody style or model to be assembled without interrupting production.

The third overhead transport system 312 carries parts or components inassembled or partially assembled condition between the variousworkstations for the underbody assembly line 306 and tack weld station.Preferably the third overhead transport system 312 is a closed loopsystem passing through each workstation of the underbody assembly line306 including the tack weld station, and through a workpiece support orantler exchange workstation. The third overhead transport system 312 canbe supplied with subassemblies from at least one subassembly line 311having an overhead transport system 313. The overhead transport systems312, 313 can be independent from one another or can be integrated into asingle overhead transport system.

The overall assembly line can also include a roof assembly line 315having a fourth overhead transport system 317. The fourth overheadtransport system 317 carries parts or components in assembled orpartially assembled condition between the various workstations for theroof assembly line 315. Preferably the fourth overhead transport systemis a closed loop system passing through each workstation of the roofassembly line 315 and through a workpiece support or outer exchangeworkstation. The fourth overhead transport system 317 can be suppliedwith subassemblies from at least one subassembly line 319 having anoverhead transport system 321. The overhead transport systems 317, 321can be independent of one another or can be integrated into a singleoverhead transport system.

The workpiece support or antler exchange workstation permits theworkpiece support or antlers for each overhead transport carriage to beexchanged depending on the automotive body style or model to be producedthrough the assembly line without interrupting production. In itspreferred form, each overhead transport system, 305, 308, 309, 310, 312,313, 317, 321 has an electric monorail system. In its most preferredconfiguration, each overhead transport system 305, 308, 309, 310, 312,313, 317, 321 is an electric monorail system having a plurality ofcarriages with a plurality of vertically extending supports or postswith lower portions moveable between a lowered position and a raisedposition. The electric monorail system conveys the carriages along apath of travel between workstations on the assembly line to convey aworkpiece to one or more workstations along the path of travel and toraise and lower the workpiece with respect to a tooling fixture,workpiece support, or geometry fixture at the various workstations asrequired. Details of the overhead transport systems 305, 308, 309, 310,312, 313, 317, 321 can be obtained from the description of FIGS. 1-11given in greater detail above.

Referring now to FIGS. 13-15, by way of example and not limitation, onepossible configuration of the overhead transport system 312 of theunderbody assembly line and tack weld station 306 is illustrated. Theconfiguration illustrated in FIG. 13 shows an electric monorail system320 with an overhead monorail 322 supporting first and second carriages324, 326 for movement along the path of travel. Vertically extendingsupports or pillars 328 extend downwardly from the first and secondcarriages 324, 326. A horizontal support member 330 extends between thevertically extending supports or pillars 328. Preferably, a single drivemechanism 332 is associated with each vertically extending support orpillar 328 for unlatching the horizontal support member 330 from alocked position with respect to the vertically extended supports orpillars 328 and for lowering the horizontal support member 330 to alowered position causing the carried workpiece to be transferred to ageometry fixture, sometimes referred to herein as a tooling fixture orworkpiece support, as required for the particular workstation. Thesingle drive mechanism 332 operates in synchronization with the othersingle drive mechanism associated with the other vertically extendingsupports or pillars 328 to raise the horizontal support member 330 fromthe lowered position and to re-latch the horizontal support member 330with respect to the vertically extending supports or pillars 328 priorto the first and second carriages 324, 326 leaving the workstation forfurther movement along the overhead rail 322.

Referring now to FIG. 14, the horizontal support member 330 preferablyprovides the ability to interchange the workpiece support or antler nest334 to match the particular automotive body style or model to beproduced on the assembly line without interrupting production. Theworkpiece support or antler nest 334 is engageable on locating pins 336located on the horizontal support member 330. The locating pinsaccurately locate the workpiece support or antler nest 334 with respectto the horizontal support member 330. Preferably, the locating pins 336include at least one outwardly driven, or biased, latch member or ballfor locking the nest 334 in position on the support member 330.Vertically extending retainer plates 338, as shown in FIG. 14C, oneither side of the horizontal support member 330 maintain the workpieceor support or antler nest 334 from lateral shifting with respect to thehorizontal support member 330. If required, a latch member can beprovided to lock the workpiece support or antler nest 334 with respectto the horizontal support member 330. The workpiece support or antlernest 334 includes transversely extending surfaces 340 defining at leastone slot or pocket 342 for engagement by an automated workpiece supportor antler nest exchange unit.

Referring now to FIGS. 14D and 14E, each end of the antler nest or crossbar 334 b can be releasibly connected to couplings 28 b, 28 c with locks400 a, 400 b at the lower ends of the telescoping posts 328 a to definethe carrier. The locks 400 a, 400 b can include housings 404 a, 404 bmounted on the lower ends of each telescoping posts 328 a of thecarrier. The carrier is formed of three parts connectible to oneanother; namely couplings 28 b and 28 c, and the antler nest or crossbar 334 b bridging the gap between the couplings 28 b and 28 c. Eachhousing 404 a, 404 b can include guide slots 406 a and 406 b forreceiving and guiding the travel of locking pins 408 a and 408 b,respectively, between an extended locking position and a retractedreleasing position. The locking pins 408 a and 408 b are connected torotatable links 410 a and 410 b, respectively. The links 410 a and 410 bare pivotally coupled together by a common pivot pin 412. A reciprocalactuator pin 414 operably engages links 410 a and 410 b adjacent thecommon pivot pin 412. The reciprocal actuator pin 414 is biased in afirst position by a biasing means 413, such as a spring, positionedbetween a washer 418 engageable with the frame 404 and a flange 420extending from the pin 414 adjacent one end. The biased position of thepin 414 corresponds to the extended, locked position of the locking pins408 a and 408 b relative to the couplings 28 b, 28 c and the antler nest334 b. The locking pins 408 a and 408 b operably engage with the guideslots 406 a and 406 b and are engageable with the slots 422 a and 422 bformed in corresponding brackets 424 a, 424 b mounted on opposite endsof the antler nest 334 b.

In operation, each end of an antler nest 334 b is engaged with acorresponding coupling 28 b, 28 c by moving the reciprocal actuator pin414 against the urging biasing of means 413 to a second position bydrive means 426. The drive means 426 can be an electric, hydraulic orpneumatic linear actuator for moving the actuator pin between the firstand second positions. As the actuator pin 414 travels from the firstposition, or locked position, to the second position, or releasedposition, the common pivot pin 412 is moved to rotate links 410 a and410 b. Contemporaneously, the locking pins 408 a and 408 b travel in theguide slots 406 a and 406 b towards each other. When the pin 414 is inthe second position, corresponding to an unlocked position between theantler nest 334 b and the couplings 28 b, 28 c, the antler nests 334 bcan be removed and exchanged by lifting movement to slide locking pins408 a and 408 b out from engagement with the brackets 424 a and 424 bthrough corresponding slots 422 a and 422 b. A new antler nest 334 b canbe replaced by directing corresponding brackets 424 a and 424 b over thelocking pins 408 a and 408 b when lowering the antler nest 334 b withrespect to the couplings 28 b, 28 c of the carrier. After the antlernest 334 b has been lowered and the locking pins 408 a and 408 b arepositioned in the slots 422 a and 422 b, the actuator pin 414 can bemoved to the first position by deactivating the drive means 426 allowingthe biasing means 413 to move the actuator pin 414 from the secondposition to the first position. As the drive means 424 moves theactuator pin 414 to the first position, the links 410 a and 410 b rotatetoward a vertically aligned position and locking pins 408 a and 408 bmove away from one another toward the ends 426 a and 426 b of the slots422 a and 422 b to lock the brackets 424 a, 424 b of the antler nest 334b to the couplings 28 b, 28 c to define the new carrier configuration.It should be recognized that the operation of the drive means could bereversed to move the actuator pin downwardly to release and upwardly tolock without departing from the scope of the present invention.Furthermore, it should be recognized that the operation of the lockingpins could be reversed to move toward one another to lock and away fromone another to release without departing from the scope of the presentinvention. The present invention provides means for coupling eachtelescoping post to a selected interchangeable antler nest. Means isprovided for releasibly locking each telescoping post with respect tothe selected one of a plurality of interchangeable antler nests, wherethe releasible locking means is moveable between a released position anda locked position. Drive means is provided for moving the locking meansbetween the released position and the locked position. Biasing meansurges the locking means toward the locked position in a normal state.

Referring now to FIGS. 15 and 16, a workpiece support or antler nestexchange workstation is provided along the path of travel of theoverhead transport system. At the exchange workstation 344, storagefacilities are provided for holding a sufficient quantity of workstationsupports or antler nests 334 to exchange out a predetermined portion, oran entire assembly line of the electric monorail system 320. As bestseen in FIG. 16, storage locations 346 can be provided for a pluralityof workpiece supports or antler nests 334 extending vertically andhorizontally along the path of travel of the overhead transport system.Storage locations 346 can be provided for the workpiece support orantler nest 334 being taken out of service, while a new workpiecesupport or antler nest 334 is taken from a storage location 346 to beput into service. One or more automated handling units 348 can beprovided for engaging members with respect to the one or more slots orpockets 342 formed in the workpiece support or antler nest 334 currentlyengaged on the horizontal support member 330. Alternatively, as shown inFIG. 16A, a robot 430 can engage an antler nest 334 c, mounted oncouplings 28 d, 28 e with locks 400 d and 400 e, by lifting the antlernest 334 c with an appropriately shaped gripper assembly. Clamps 431 a,431 b can be provided on the gripper assembly for grasping the antlernest during the exchange and transport process. If required, thecorresponding latch or latches are disengaged to release the workpiecesupport or antler nest 334 from the horizontal support member 330. Theautomated handling unit 348 then lifts the workpiece support or antlernest 334 from the locating pins 336 to disengage the workpiece supportor antler nest 334 from the horizontal support member 330. After theworkpiece support or antler nest 334 is disengaged from the horizontalsupport member 330, the workpiece support or antler nest 334 can bepositioned in an empty storage location 346. Depending on the speed ofthe overhead transport system, the same automated handling unit, or adifferent automated handling unit, at the same exchange workstation, orat a second exchange workstation, can locate and retrieve the desirednew workpiece support or antler nest 334 from the corresponding storagelocation 346. The automated handling unit 348 removes the workpiecesupport or antler nest 334 from the storage location 346 and positionsthe workpiece support or antler nest 334 directly above the locatingpins 336 on the horizontal support member 330. The automated handlingunit 348 lowers the new workpiece support or antler nest 334 onto thelocating pins 336 to position the workpiece support or antler nest 334with respect to the horizontal support member 330. If required, a latchor multiple latches are actuated to lock the workpiece support or antlernest 334 with respect to the horizontal support member 330. The overheadtransport system then can move the trolley or workpiece carrier 350 fromthe exchange loading station to the next station along the path oftravel of the overhead rail 322. The process is then repeated for eachsuccessive trolley 350 delivered to the exchange workstation as requiredfor a portion of or the complete number of trolleys existing in theoverhead transport system as required for the particular automotive bodystyle or model to be assembled.

Referring now to FIG. 16A, an exchange workstation 344 a is provided toexchange an antler nest 334 b. Storage facilities can be provided at theexchange workstation 344 a for holding a sufficient quantity of antlernests 334 b, of the same or different configurations as required, toexchange out a predetermined portion, or an entire assembly line of theelectric monorail system 320. Storage locations similar to storagelocations 346 can be provided for each antler nest 334 b extendingvertically and horizontally along the path of travel of the overheadtransport system. Empty storage locations can be provided for storing aworkpiece support or antler nest 334 b being taken out of service, whilea replacement workpiece support or antler nest 334 b is taken fromanother storage location and put into service. The exchange workstation344 a can exchange antler nests 334 b having locks 400. The exchangeworkstation 344 a can have a plurality of drive means 426 for releasingeach lock engaging the antler nest 334 b with the telescoping posts 328a through couplings 28 c and 28 b. FIGS. 14D and 14E provide a detailedillustration of this engagement. The exchange workstation 344 a caninclude one or more automated exchange units 430 for lifting an antlernest 344 b away from the telescoping posts 328 a of the carrier. Theunit 430 can include jaws 431 a and 431 b to grasp the antler nest 334 band disengage the antler nest 334 b from the coupling 28 c and 28 b ofthe carrier.

Referring now to FIG. 17, the trolley or workpiece carrier 350 can stopat one or more manual or automated loading stations 352. The loadingstation 352 can be located before the first flexible body assemblyworkstation, or in between flexible body assembly workstations asrequired. At the manual loading station 352 as illustrated in FIG. 17,parts can be supplied in quantity for manual placement with respect tothe workpiece support or antler nest 334 carried by the trolley 350.Referring now to FIG. 18, an automated loading/unloading station 354 isillustrated. The overhead electric monorail system 320 delivers thetrolley 350 to the workstation. If required, the horizontal supportmember 330 is lowered by single drive mechanisms 332 (FIG. 13) fortransferring the supported workpiece or component to a stationaryworkpiece support or geometry fixture (not shown) at the workstation.Automated equipment, such as one or more robots 356, can be used totransfer parts to and from the overhead electric monorail system 320with respect to a second part or component delivery system 358. Aplurality of predefined fixtures 360 can be provided for each robot 356or automated loading and unloading equipment in order to properly engageand hold the current workpiece corresponding to a particular automotivebody style or model for transfer from one transport system to the other.This action can be performed to load the overhead monorail system 320,or to unload the overhead monorail system 320. The predefined fixtures360 can be changed as required for meeting the production requirementsof the particular automobile bodystyle or models to be manufacturedthrough the assembly line.

Referring now to FIGS. 19-20, a flexible body assembly workstation isillustrated in detail. This workstation can be one of a plurality alonga single overhead transport system 308, 310, 312, for assembly of theleft hand bodyside, right hand bodyside or underbody assembly lines 302,304, 306 respectively. Various modifications can be made to the flexiblebody assembly workstation without departing from the disclosure of thepresent invention. By way of example and not limitation, the number,type, and location of the automated robots can be changed and modifiedas required for the particular workstation depending on the work to beperformed. By way of example and not limitation, the flexible bodyassembly workstation can perform the function of a geometry workstation,a respot workstation, a loading or unloading station, a sealer station,a stud welding workstation, a MIG welding workstation, and a productinspection workstation. The flexible body assembly workstation 362preferably includes one or more robots 364 positioned on either anoverhead gantry or platform and/or at floor level, as required for theparticular function to be performed at the workstation 362. The flexiblebody assembly workstation 362 also includes an overhead electricmonorail system 320 extending through the workstation for deliveringparts, or partially assembled components for further assembly at theworkstation. As previously described, the electric monorail system 320includes an overhead rail 322 supporting a trolley or workpiece carrier350 by first and second carriages 324, 326 connected to the overheadrail 322. Vertically extending supports or pillars 328 extend downwardlyfrom each carriage 324, 326 to support a horizontal support member 330there between. A workpiece support or antler nest 334 is operablyengaged with the horizontal support member 330. A single drive mechanism332 is provided for each vertically extending support or pillar 328 toengage and unlock the horizontal support member 330 from the verticallyextending supports or pillars 328 prior to being lowered into a loweredposition to transfer the workpiece or component from the antler nest 334to a geometry fixture, sometimes referred to herein as a tooling fixtureor workpiece support, located at the flexible body assembly workstation362. The flexible body assembly workstation 362 includes workpiecesupport or geometry fixtures corresponding to the number of differentautomotive body styles and/or models to be produced through the assemblyline. Workpiece supports or geometry fixtures 366 a, 366 b, 366 c, 366 dare illustrated to correspond to each of four automotive body stylesand/or models respectively to be built through the flexible bodyassembly workstation 362. The workpiece support or geometry fixtures canbe moved relative to the flexible body assembly workstation 362 in orderto bring the appropriate workpiece support or geometry fixture intoposition to receive the carried workpiece or a component from thetrolley 350. Providing a single geometry fixture at each workstation forthe particular body style or model to be assembled eliminates variationbetween the geometry of successively assembled parts passing through theworkstation, as is commonly experienced with systems based on a palletdelivery configuration. Consistency between the component parts isdesirable to achieve the quality standards and tolerances required byautomotive manufacturers. Since each workpiece or component is placedinto the same geometry fixture corresponding to the same body style ormodel to be assembled, consistent part production and improved tolerancespecifications can be met with the present invention. As the horizontalsupport member 330 of the trolley 350 is lowered into the lowerposition, the supported workpiece or component is transferred from theworkpiece support or antler nest 334 to the corresponding geometryfixture, such as 366 a, corresponding to the style or model to beassembled. The workpiece support geometry fixtures 366 a, 366 b, 366 c,366 d, are moveable along a predetermined path to change the geometryfixtures as required for the product mix being assembled through theworkstation 362. By way of example and not limitation, the geometryfixtures can be supported on a roller conveyor for movement along apredetermined horizontal path to locate any one of the geometry fixturesin the operable position or ready position below the overhead rail 322for receiving the next delivered workpiece or component by the trolley350 entering the flexible body assembly workstation 362. The geometryfixture handling system 368, such as roller conveyor 370 can exchangethe furthest apart geometry fixtures, by way of example and notlimitation 366 a and 366 d with each other within the cycle timepermitted for the removal of a finished workpiece or component from theworkstation 362 and the delivery of the next workpiece or component tothe flexible body assembly workstation 362.

An alternative geometry fixture handling system 368 is illustrated inFIGS. 21, 22 and 23. An “H-Gate” configuration is illustrated in FIGS.21-23. In this configuration, a rail shuttle system 372 is providedpassing through the center line of the flexible body workstation 362 inorder to move a geometry fixture 366 a from the operable position orready position to a standby position 374 on either side of the operableposition 376 along the rails 378. On either side of the workstation 362,transversely extending fixture delivery systems 380 extend on eitherside of the rails 378. This configuration gives the fixture deliveryhandling system 368 its distinctive “H” moniker. The fixture deliveryconveyors 380 can include one or more geometry fixtures 366 a, 366 b,366 c for delivery to the operable position 376. The H-Gate systemdelivers a new geometry fixture 366 a to the standby position 374. Afterwork has been completed on the workpiece at the flexible body assemblyworkstation 362 in the operable position 376, and the workpiece has beenlifted from the geometry fixture 366 b, the shuttles 382, 384 arereciprocated along the rails 378 to move the previously used geometryfixture 366 b from the operable position 376 to a standby position 374,while the geometry fixture 366 a is moved from the standby position onthe opposite side of the workstation 362 to the operable position 376.The previously used geometry fixture 366 b can then be removed from theshuttle while at the standby position 374. As illustrated in FIG. 22,the overhead transport system 320 can deliver the workpiece or acomponent to the geometry fixture located at the operable position 376,while the next to be used geometry fixture is positioned at the standbyposition 374. When required, the shuttles can be reciprocated along therails 378 to move the previously used geometry fixture from the operableposition 376 while being replaced with the new geometry fixture from thestandby position 374.

Referring now to FIG. 23, the overhead transport system is illustratedfor lowering a part or component onto the geometry fixture waiting atthe operable position 376. One or more automated robots 356 are providedfor performing assembly work on the part or component delivered to theoperable position 376. The fixture delivery conveyors 380 can be seenfor moving the geometry fixtures to and from the standby position oneither side of the flexible body assembly workstation 362.

Referring now to FIGS. 24A-24D, alternative configurations for theH-Gate geometry fixture delivery system are provided illustrating asingle geometry fixture configuration 386 in FIG. 24A, a dual geometryfixture handling system or H-Gate 388 in FIG. 24B, a triple geometryfixture handling system or H-Gate 390 in FIG. 24C, and a quadruplegeometry handling system or H-Gate 392 in FIG. 24D. This configurationis extremely flexible for providing flexible body assembly workstationscapable of handling single automotive body styles or models, dualautomotive body styles or models, three different automotive body stylesor models, and up to four different automotive body styles or models.

Using either geometry fixture handling system 368, the flexible bodyassembly workstation 362 according to the present invention provides asingle geometry fixture for each automotive body style or model to bemanufactured through the workstation. This increases the reliability,repeatability, and manufacturing tolerances capable of being achievedthrough the flexible body assembly workstation 362. The flexible bodyassembly workstation 362 also increases manufacturing efficiency, byallowing a product mix to be handled through the assembly line withoutdown time for retooling.

Referring now to FIG. 25, the present invention includes the transfer ofthe underbody assembly from the overhead transfer system 312 to apalletized system 394, such as that shown in FIG. 25. The palletizedsystem provides a pallet that receives the workpiece or components to beassembled and the pallet remains with the workpieces as the workpiecetravels along the rail system through the underbody respot workstation,framing workstation, framing respot workstation, closure workstation,and painting workstation. The underbody respot workstation can include aplurality of robots 398 for welding areas inaccessible during thetacking at the underbody tack workstation. Additional details regardingthe framing workstations can be obtained from International PublicationNumber WO 99/24215 published on May 20, 1999 which is incorporated byreference herein.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiments but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims, which scope is to be accorded the broadestinterpretation so as to encompass all such modifications and equivalentstructures as is permitted under the law.

What is claimed is:
 1. An apparatus for assembling different automotivebody styles on a single assembly line comprising: means for transportingautomotive components along a predetermined path for delivery through atleast one workstation, each of the components corresponding to one of aplurality of different automotive body styles to be processed on theassembly line; means for selectively positioning one of a plurality ofgeometry fixtures at a ready position of the at least one workstation toreceive the automotive component from the transporting means, the readyposition located along a positioning path of travel extendingtransversely to the predetermined path for delivery of the transportedautomotive components, each of the plurality of geometry fixturescorresponding to a different body style of the plurality of automotivecomponents to be transported along the path; means for transferring theautomotive component between the geometry fixture at the ready positionand the transporting means; and means for preventing the transportingmeans from moving with respect to the at least one workstation ifmovement of the transferring means has failed to transfer the automotivecomponent from the geometry fixture to the transporting means, whereinthe preventing means includes at least one sensor mounted to thetransporting means for generating a vertical position signalcorresponding to a vertical position of the transferring means withrespect to the transporting means, and drive means, responsive to thevertical position signal from the sensor based on a control programstored in memory, for controlling movement of the transporting means. 2.The apparatus of claim 1 further comprising: position control means formoving a selected geometry fixture to the ready position within a timeperiod cycle corresponding to moving a first component out of the atleast one workstation and delivering a second component to the at leastone workstation while different automotive body styles are beingassembled in sequence concurrently on the assembly line.
 3. Theapparatus of claim 2 wherein the position control means furthercomprises: means for generating a configuration signal corresponding toan automotive component to be delivered to the at least one workstationnext; and drive means, responsive to the configuration signal based on acontrol program stored in memory, for moving a geometry fixturecorresponding to the particular automotive body style to be delivered tothe at least one workstation next to the ready position.
 4. Theapparatus of claim 1 further comprising: means for stopping thetransporting means when the transporting means reaches the workstation.5. The apparatus of claim 1 further comprising: means for guiding thetransporting means into the at least one workstation to align thetransporting means with respect to the geometry fixture at the readyposition.
 6. The apparatus of claim 1 wherein the transporting meansfurther comprises: a trolley movable along the path; and a carriagemovable between a raised position and a lowered position relative to thetrolley.
 7. The apparatus according to claim 1 further comprising: atleast one robot at the workstation for performing a processing operationon the automotive component delivered to the geometry fixture at theready position of the workstation.
 8. The apparatus of claim 1 whereinthe transferring means are located separate from the transporting meansat each workstation.
 9. The apparatus of claim 1 further comprising: atleast one elevated robot located at said workstation along thepredetermined path for performing work on the transported automotivecomponents; and the geometry fixtures moveable along the positioningpath located at an elevation below the at least one elevated robot. 10.An apparatus for assembling different automotive body styles on a singleassembly line comprising: means for transporting automotive componentsalong a predetermined path for delivery through at least oneworkstation, each of the components corresponding to one of a pluralityof different automotive body styles to be processed on the assemblyline, wherein the transporting means includes a trolley movable alongthe path, and a carriage movable between a raised position and a loweredposition relative to the trolley; means for selectively positioning oneof a plurality of geometry fixtures at a ready position of the at leastone workstation to receive the automotive component from thetransporting means, each of the plurality of geometry fixturescorresponding to a different body style of the plurality of automotivecomponents to be transported along the path; and means for transferringthe automotive component between the geometry fixture at the readyposition and the transporting means, wherein the transferring meansincludes a lowerator having a rotatable lifter arm with a rollerdisposed adjacent an outer end of the lifter arm, the lifter armrotatable from a first angular position through a second angularposition to a third angular position, such that as the lifter armrotates from the first position to the second position the rollerengages the carriage, releases a latch maintaining the carriage in theraised position, and as the lifter arm rotates from the second positionto the third position lowers the carriage to transfer the automotivecomponent to the geometry fixture at the ready position when thecarriage is in the lowered position.
 11. The apparatus of claim 10further comprising: means for preventing the transporting means frommoving with respect to the at least one workstation if movement of thetransferring means has failed to transfer the automotive component fromthe geometry fixture to the transporting means.
 12. The apparatus ofclaim 10 further comprising: lowerator drive means for rotating thelifter arm from the first position to the third position when thecarriage is at the ready position, and to rotate the lifter arm from thethird position to the first position in response to a signal indicatingthat a processing operation has been completed at the workstation. 13.The apparatus of claim 12 wherein the lowerator drive means furthercomprises: a sensor operable to emit a trolley-present signal when thetrolley reaches the workstation above the geometry fixture in the readyposition; and means for operating the lowerator in response to thetrolley-present signal based on a control program stored in memory. 14.The apparatus of claim 13 wherein the lowerator drive means furthercomprises: a sensor to emit a carriage-lock signal and a carriage-unlocksignal; and control means, responsive to the carriage-lock signal andthe carriage-unlock signal based on a control program stored in memory,for rotating the lifter arm from the first position to the secondposition if the carriage-lock signal is initially present, and tocontinue rotating the lifter arm from the second position to the thirdposition if the carriage-lock signal changes to the carriage-unlocksignal.
 15. A method of assembling different automotive body styles on asingle assembly line comprising the steps of: transporting automotivecomponents along a predetermined path through at least one workstationwith transporting means, each of the components corresponding to one ofa plurality of different automotive body styles to be processed on theassembly line; selectively positioning with positioning means one of aplurality of geometry fixtures at a ready position of the at least oneworkstation to receive the automotive component from the transportingmeans, the ready position located along a positioning path of travelextending transversely to the predetermined path for delivery of thetransported automotive components, each of the plurality of geometryfixtures corresponding to a different body style of the plurality ofautomotive components to be transported along the path; transferring theautomotive component between the geometry fixture and the transportingmeans with transferring means; and controlling the positioning means tomove a selected geometry fixture to the ready position within a timeperiod cycle defined between a first component being transported awayfrom the workstation and a second component arriving at the workstationwhile different automotive body styles are being assembled in sequenceconcurrently on the assembly line, wherein the controlling step furtherincludes the steps of receiving a configuration signal corresponding tothe automotive body style to be delivered to the workstation next withelectronic control means, and controlling the positioning means to movea geometry fixture to the ready position corresponding to the automotivebody style to be delivered next to the workstation based on theconfiguration signal with the electronic control means and a controlprogram stored in memory.
 16. The method of claim 15 further comprisingthe step of: controlling the transporting means to prevent thetransporting means from moving with respect to the workstation ifmovement of the transferring means has failed to transfer the automotivecomponent from the geometry fixture to the transporting means.
 17. Themethod of claim 15 further comprising the step of: controlling thetransferring step to prevent transfer of the automotive component fromthe transporting means to the geometry fixture until the geometryfixture is located at the ready position.
 18. A method of assemblingdifferent automotive body styles on a single assembly line comprisingthe steps of: transporting automotive components along a predeterminedpath through at least one workstation with transporting means, each ofthe components corresponding to one of a plurality of differentautomotive body styles to be processed on the assembly line; selectivelypositioning with positioning means one of a plurality of geometryfixtures at a ready position of the at least one workstation to receivethe automotive component from the transporting means, each of theplurality of geometry fixtures corresponding to a different body styleof the plurality of automotive components to be transported along thepath; transferring the automotive component between the geometry fixtureand the transporting means with transferring means; and controlling thetransporting means to prevent the transporting means from moving withrespect to the workstation if movement of the transferring means hasfailed to transfer the automotive component from the geometry fixture tothe transporting means, wherein the step of controlling the transportingmeans includes the steps of receiving a vertical position signalcorresponding to the vertical position of the transferring meansrelative to the transporting means with an electronic control means, andcontrolling the transporting means to stop with the electronic controlmeans if the transferring means has failed to transfer the automotivecomponent from the geometry fixture to the transporting means based onthe vertical position signal in accordance with a control program storedin memory.
 19. A method of assembling different automotive body styleson a single assembly line comprising the steps of: transportingautomotive components along a predetermined path through at least oneworkstation with transporting means, each of the componentscorresponding to one of a plurality of different automotive body stylesto be processed on the assembly line; selectively positioning withpositioning means one of a plurality of geometry fixtures at a readyposition of the at least one workstation to receive the automotivecomponent from the transporting means, the ready position located alonga positioning path of travel extending transversely to the predeterminedpath for delivery of the transported automotive components, each of theplurality of geometry fixtures corresponding to a different body styleof the plurality of automotive components to be transported along thepath; transferring the automotive component between the geometry fixtureand the transporting means with transferring means; and controlling thetransferring step to prevent transfer of the automotive component fromthe transporting means to the geometry fixture until the geometryfixture is located at the ready position, wherein the step ofcontrolling the transferring step further includes the step of receivinga transporting-means-present signal corresponding to the transportingmeans being positioned at the workstation above the geometry fixturepositioned at the ready position with an electronic control means,receiving a fixture-present signal corresponding to the geometry fixturepositioned at the ready position with the electronic control means, andcontrolling the transferring means with the electronic control meansbased on the transporting-means-present signal, the fixture-presentsignal in accordance with a control program stored in memory.
 20. Themethod of claim 19 further comprising the step of: controlling thepositioning means to move a selected geometry fixture to the readyposition within a time period cycle defined between a first componentbeing transported away from the workstation and a second componentarriving at the workstation while different automotive body styles arebeing assembled in sequence concurrently on the assembly line.
 21. Themethod of claim 19 further comprising the step of: controlling thetransferring step in response to a signal indicating if the transferringmeans is locked in a raised position relative to the transporting means.22. A method of assembling different automotive body styles on a singleassembly line comprising the steps of: transporting automotivecomponents along a predetermined path through at least one workstationwith transporting means, each of the components corresponding to one ofa plurality of different automotive body styles to be processed on theassembly line; selectively positioning with positioning means one of aplurality of geometry fixtures at a ready position of the at least oneworkstation to receive the automotive component from the transportingmeans, each of the plurality of geometry fixtures corresponding to adifferent body style of the plurality of automotive components to betransported along the path; transferring the automotive componentbetween the geometry fixture and the transporting means withtransferring means; and controlling the transferring step in response toa signal indicating if the transferring means is locked in a raisedposition relative to the transporting means, wherein the controllingstep includes the steps of receiving the signal indicating thetransferring means is locked in the raised position with electroniccontrol means, engaging the transferring means to rotate a lifter armfrom a first position to an intermediate position with the electroniccontrol means, determining if the signal is interrupted when the lifterarm is rotated to the intermediate position with the electronic controlmeans, continuing engagement of the transferring means to rotate thelifter arm from the intermediate position to a second position with theelectronic control means if the signal has been interrupted when thelifter arm is rotated to the intermediate position from the firstposition with the electronic control means, receiving a signalcorresponding to a completion of work at the workstation with theelectronic control means, engaging of the transferring means to rotatethe lifter arm from the second position to the first position with theelectronic control means, and determining if the signal is receivableafter the lifter arm has been rotated from the second position to thefirst position with the electronic control means.
 23. An apparatus forassembling different automotive body styles on a single assembly linecomprising: overhead means for transporting automotive components alonga predetermined path for delivery through at least one workstation, eachof the components corresponding to one of a plurality of differentautomotive body styles to be processed on the assembly line; means forselectively positioning one of a plurality of geometry fixtures at aready position of the at least one workstation to receive the automotivecomponent from the overhead transporting means, each of the plurality ofgeometry fixtures corresponding to a different body style of theplurality of automotive components to be transported along the path; andmeans, located separate from the overhead transporting means at eachworkstation, for transferring the automotive component between thegeometry fixture at the ready position and the transporting means,wherein the transferring means further includes a lowerator having arotatable lifter arm with a roller disposed adjacent an outer end of thelifter arm, the lifter arm rotatable from a first angular positionthrough a second angular position to a third angular position, such thatas the lifter arm rotates from the first position to the second positionthe roller engages the overhead transporting means, releases a latchmaintaining the overhead transporting means in a raised position, and asthe lifter arm rotates from the second position to the third positionlowers the overhead transporting means to transfer the automotivecomponent to the geometry fixture at the ready position when theoverhead transporting means is in a lowered position.
 24. The apparatusof claim 23 further comprising: the ready position located along apositioning path of travel extending transversely to the predeterminedpath for delivery of the transported automotive components.
 25. Theapparatus of claim 23 further comprising: at least one elevated robotlocated at said workstation along the predetermined path for performingwork on the transported automotive components; and the geometry fixturesmoveable along a positioning path located at an elevation below the atleast one elevated robot.